Stociometry

Question 1

Molar mass

Answer 1

The mass of 1 mole of a substance

Question 2

1 mole equals how many atoms

Answer 2

6.022 x 10^23 atoms/units

Question 3

What is the Relative Atomic Mass of atoms

Answer 3

The average of all isotopes that is usually found, also usually the atomic mass stated on an element/ Average mass of a molecule

Question 4

Formula for finding relative atomic mass

Answer 4

Isotope A’s mass x Relative abundance of A’s atoms (decimals) + Isotope B’s mass x Relative abundance of B’s atoms (decimals)

Question 5

What are the steps a Mass Spectromy machine uses to find the mass/charge ratio of an elements isotopes

Answer 5

Ionization: Knocks off or adds electrons
Acceleration: Speeds up ions to same speed
Deflection: Uses positive and negative magnets to deflect ions based on mass and ionization
Detection: Ion beam is detected electrically

Question 6

Steps to balance an equation

Answer 6

1. Write out equation
2. List elements; Hydrogens and Oxygens last
3. Balance 1 element w/ coefficients
4. Check to see if equation is balanced
5. Repeat till balanced fully

Question 7

Formula for finding the moles of an element

Answer 7

Moles = Mass/Molecular mass

Question 8

What is Molecular Mass

Answer 8

The addition of all atomic masses in a molecule

Question 9

Ex. What is the number of moles in 35.0g of CuSO4?

Answer 9

Moles = Mass/Molecular mass

35.0g/(63.5 + 32.0 + 16.0 x 4) = 0.219 moles

Question 10

Ex. What is the number of moles in 75.0mg of CaSO4 H2O?

Answer 10

Moles = Mass/Molecular mass

0.075 (mg are 100x smaller than g)/(40 + 32.0 + 16.0 x 4 + 18.0 x 2) = 4.36 x 10^ -4

Question 11

Ex How many chloride ions are there in a 25.0 cm of a solution of magnesium chloride (MgCl) w/ a concentration of 0.400 mol/dm^3

Answer 11

Molar concentration = Concentration x Volume (M = C x V)

1. MgCl2 = 0.400 x 0.0250 = 0.0100 moles of chlorine ions
2. 0.0100 x 2 (Since there are 2 chlorine ions for every one mole of MgCl2)
   = 0.0200 moles
3. Moles of chlorine ions x Avogadro’s number = 4.36 x 10^-4

Question 12

Which version of the formula to find the number of moles is for solutions

Answer 12

Moles = concentration x volume

(C = M/V, V = M/C)

Question 13

Which version of the formula to find the number of moles is used for pure solids, liquids, and gases only?

Answer 13

Moles = Mass/Molecular mass

(M = Mol x Mr, Mr = Mol x M)

Question 14

1 mole = ?

Answer 14

The molar mass (Atomic mass of one atom of an element)